1. Field of the Invention
The present invention relates to an optical-sheet supporting structure, a lighting device and a display device.
2. Description of the Related Art
A backlight device used for a liquid-crystal display device or the like is widely known, and includes an optical component having a plurality of optical sheets stacked on a panel, such as a diffuser plate or a light guide plate (as described in JP-A-2002-341345, for example). The optical component is disposed on the front or side of a light source in order that light from the light source may be uniformly radiated to a liquid-crystal panel. A structure shown in FIG. 7 is provided as an example of its supporting structure, which supports a panel 10 and optical sheets 11 by sandwiching in the periphery thereof between a base member 15 and a holding member 16. According to this supporting structure, assembly can be readily achieved by simply laying the parts on top of one another.
In the supporting structure, preferably, a predetermined gap is formed between the holding member 16 and the optical sheets 11. In the case that the optical sheets 11 are held so as to be subjected to direct intense pressure, the optical sheets 11 may vault (See FIG. 8) when the optical sheets 11 expand or contract due to change of ambient temperature or the like. This could result in failing to uniformly radiate light from the light source to the liquid-crystal panel. However, actually the holding member 16 may apply direct pressure on the optical sheets 11 due to the following two reasons, and this should be improved.
The first reason is that the panel 10 can move due to the gap. That is, when the backlight device is used in an upright orientation, for example, the panel 10 may lean forward within the gap (or play) provided between the holding member 16 and the optical sheets 11. In recent years in particular, panels 10 have been getting larger along with increasing size of display devices. Therefore, once the panel 10 leans forward, the periphery of the optical sheets 11 may be sandwiched in between the leaning panel 10 and the holding member 16 so as to be subjected to intense pressure.
The second reason is that the holding member 16 can lean inwardly. Other components may be disposed on the holding member 16. In this case, if the holding member 16 is not adequately supported, the distal end portion 16A thereof may lean inwardly (See FIG. 9). In recent years in particular, components have been growing in size. This could result in increasing the tendency of the holding member 16 to be made of resin. In this case, high-accuracy components cannot be expected, and therefore the gap between the holding member 16 and the optical sheets 11 may be originally narrower than designed. In this instance, the distal end portion 16A of the holding member 16 may apply intense pressure on the periphery of the optical sheets 11, if it leans inwardly as described above.